1. Field of the Invention
The present invention relates to the insertion of codes or binary messages of identification or authentication in digital moving pictures and, more specifically, in moving pictures compressed by a motion calculation, area by area, from one picture to the other, for example, according to the Standard MPEG2, MPEG4, or H263.
2. Discussion of the Related Art
A first example of application relates to the insertion of an identifier or the person entitled to the rights relative to the video sequence to enable detection of a possible piracy by distribution of illicit copies. A second example of application is the protection against set-ups deforming or falsifying the pictures of video sequences, to ensure the integrity of a film. A third example is the insertion of rights relative to the use of the video sequences (number of copies or of possible uses).
The technique of binary code insertion in digital pictures is generally known as the “watermarking” and has had a recent expansion with the rapid development of digital picture transmission, especially over the Internet. Considering the increasing risk of illicit copies, the persons entitled to royalties, in particular, have searched for means to protect moving digital multimedia contents.
The three above examples concern so-called security applications. Non-security applications may also be found, for example, the inserting of characteristics linked to the shooting or other picture information.
Generally, the inserting of a code concerns each picture in the animated sequence, all pictures then comprising an insertion (for example, an identification code of the author is reproduced in all pictures). It is possible for the content of the respective codes to be linked to the picture sequence, to detect a possible parasitic picture insertion.
Whatever the application, a so-called marking algorithm is used to encrypt and position, in the pictures, the codes to be inserted therein. A reverse algorithm is used to restore, according to the application, the identification codes or the shooting characteristics, etc.
Many moving picture marking algorithms are known, for example, of standard ISO/IEC 13818-2 “Generic Coding of Moving Pictures and Associated Audio”. The present invention does not relate to the actual marking algorithm and applies whatever the type of algorithm used.
The modification or coding often takes the form of an addition of a specific noise forming the hidden message. In the case of moving pictures to which the present invention applies, this noise addition results, especially if a marking robustness requiring stronger marking is desired, in a flickering of the pictures which is unacceptable in practice.
It could be devised not to mark all the pictures, to reduce the perception of the flickering by a human eye. However, such a solution would considerably weaken the marking, in particular to guarantee the picture sequence integrity.